This section provides background information related to the present disclosure which is not necessarily prior art.
A spark plug typically includes a housing configured to thread into a spark-plug hole of an engine, a center electrode extending axially from the center of the housing, and a ground electrode extending radially inward from the housing. When the spark plug is installed in the engine, the center electrode and the ground electrode are exposed to gas within a cylinder of the engine. The spark plug generates a flame kernel between the center electrode and the ground electrode, and the resulting flame is propagated through the cylinder.
A pre-chamber spark plug includes a pre-chamber cup attached to the housing and enclosing the center electrode and the ground electrode. During an intake stroke, unburned gas flows through one or more orifices extending axially through the bottom surface of the pre-chamber cup. At combustion, the pre-chamber spark plug ignites the unburned gas by generating a spark between the center electrode and the ground electrode. During a power stroke, a flame jet resulting from the spark flows through the orifices and ignites unburned gas within the cylinder outside of the pre-chamber spark plug.